For a conventional image display unit such as a cathode-ray tube (CRT) or a field emission display (FED), a metal back-attached phosphor screen which has a metal film formed on the inner surface (surface opposite to the face plate) of a phosphor layer has been used extensively.
Such a metal film is called the metal back layer and it reflects light advancing to an electronic source, which is in light emitted from a phosphor material by electrons emitted from the electronic source, toward the face plate to enhance brightness and also serves to stabilize the potential of the phosphor layer as an anode electrode. And, the metal back also has a function to prevent the phosphor layer from being damaged by ions which are generated when gas remaining in a vacuum envelope is ionized.
Particularly, the FED had a disadvantage that an electric discharge (vacuum arc discharge) occurred easily when images were formed for a long period because there was a small gap (space) of approximately one to several millimeters between the face plate having a phosphor screen and a rear plate having electron emission elements, and a high voltage of approximately 10 kV was applied to the very small gap to form a high electric field.
And, when such an abnormal electric discharge occurred, a large discharge current in a range of several amperes to several hundred amperes flowed instantaneously, so that there was a possibility that electron emission elements of a cathode section and a phosphor screen of an anode section were destructed or damaged.
In order to ease a damage in case of the occurrence of an abnormal electric discharge, there is proposed an image display having a metal back layer (an anode electrode) in which gaps are formed in a zigzag form (meandering form) or a spiral form (coil form) in Japanese Patent Laid-Open Applications No. 2000-311642, No. 2000-251797, No. 2000-326583, etc. And, there is proposed a method of cutting with laser or vapor deposition with a metal mask for fabricating and forming the anode electrode into a zigzag form or the like.
But, the image display had disadvantages that it required an expensive and large-scale device such as a laser generator in order to cut and fabricate the anode electrode and that an effect of preventing an electric discharge from occurring between the anode section and the cathode section was insufficient.
The present invention has been made to remedy the above-mentioned disadvantages and provides a method for forming a metal back-attached phosphor screen which prevents electron emission elements and a phosphor screen from being destructed or deteriorated by an electric discharge and an image display unit capable of making highly bright and high quality display without having the deterioration of brightness.